X-ray tube



" Feb. El, 1936. v J ANDREW 7 2,039,561

X-RAY TUBE! Filed March 28, 1935 INVENTOR Patented Feb. 11, 1936 UNITED STATES PATENT OFFICE X-BIAY TUBE Application March 28, 1933, Serial No. 663,130

2 Claims.

This invention relates to electrical discharge devices and more particularly to devices of the character adapted to be employed in the production of X-rays and commonly termed X-ray tubes. In its more specific aspect the invention is directed to an X-ray tube having a movable target.

Heretofore it has been proposed to construct X-ray tubes with rotating targets. My invention dififers from the structures of the prior art in that I have provided a novel type of anode having means for cooling the same.

Briefly stated, my invention comprises an X-ray tube including a novel anode, a cathode, said anode comprising a stationary member and a rotatable member being so designed with respect to each other as to provide for adequate cooling of the rotatable member.

An object of my invention is to provide a new and improved X-ray tube.

Another object of my invention is to provide a novel anode for an electron discharge device of novel design.

Another object of my invention is to provide a novel type of electrode cooling means.

Another object of my invention is to provide a novel type of electrode.

Other objects and advantages of my invention will become readily apparent from the following specification and drawing wherein:

The single figure represents a fragmentary longitudinal cross-sectional view with some of the parts in elevation and other parts in section of an X-ray tube embodying my invention.

According to my invention the X-ray tube comprises a dielectric enclosing elongated and evacuated envelope It having a reentrant tube II at one end and a reentrant tube l2 at its other end. The reentrant tube I2 has a press I3 at the free end thereof in which press are hermetically sealed leading-in conductors l4 and I5 having portions thereof extending interiorly and exteriorly of said envelope. A dielectric cylinder It has one end thereof fusedly ring-sealed (not shown) to the reentrant tube [2 or to the body of the envelope Ill. This cylinder It extends along, is concentric with the reentrant tube l2 and has its free end located slightly below the press l3.

Secured to said free end of said cylinder 16 is a metallic focusing cup l'i which surrounds the press l3 and extends an appreciable distance thereabove. The upper end of said cup is in the form of a concave plate [8 whose face is complementary to the face of the target hereafter described. The plate I8 has an oblong shaped opening therein extending along the hypotenuse describing the same and is of appropriate dimensions depending upon the size of the focal spot to be obtained on the target of the anode. Electrically secured to said cup I! is the leading-in conductor M and one end of a thermionic filamentary cathode W of the type disclosed in the copending application entitled Line focus cathode structure of Louis F. Ehrke, Serial No. 622,424 filed July 14, 1932 and assigned to the same assignee as the present invention. The other end of said cathode I 9 is connected to the leading-in wire 15. The cathcde'is disposed substantially parallel to the plate l8.

To the free end of the reentrant tube II is secured an anode comprising a stationary member and rotatable member 2|. The member 20 constitutes a stationary portion of the anode for rotatabLy supporting the rotatable or movable portion of the anode. In the specific example shown, the device comprises an X-ray tube in which the movable portion of the anode constitutes the support for the target of the X-ray tube.

My invention is primarily related to a simple structure which will permit rotation of the target and dissipation of the heat developed at the target by means of radiation. With this principle in mind, and which has not heretofore been taken advantage of in the esign of X-ray tube rotating targets and their cooling means, I have provided the anode comp-rising the stationary member 29 and the rotatable member 2|. The rotatable member consists essentially of a rather shallow cone or target portion 22 having a heat radiating portion in the form of a plurality of cylindrical sheets or plates, and as shown, four concentrically spaced cylinders 23, 24,25 and 26 integral with and of the same composition, copper, as the cone 22. The cone 22 is recessed along the major portion of the outside area thereof to provide a space in which a conical plate 2'! of tungsten or other good X-ray emitting material is secured thereto. The tungsten cone 2'1 is thin and is so secured to the copper backing 22 to be in good thermal and electrical contact therewith.

The cylinders 23, 24, 25 and 26 integral with the backing 22 are relatively thin and are of such diameters as to provide an annular space 50 between adiacent pairs of cylinders that is equal to about 5 times the thickness of each cylinder. The outermost cylinder 23 is recessed and in said recess is secured a cylinder 28 composed of soft iron or other material that is easily magnetized.

To the inner surface of the innermost cylinder 26 at the upper and lower ends respectively thereof are secured ball bearing race rings 29 and 29.

The stationary member 20, of copper or the like, may be in the form of a copper chamber having its closed end in the form of a plurality of concentric cylindrical sheets or plates 3t, 31, 32, 33, 34 and 35 with the lower ends of the cylinders 30-3I, 3233, and 3435 and the upper ends of the cylinders 34-42, and 33-34 being closed and forming a looped arrangement in cross section, as shown.

The upper end of the innermost cylinder 35 is cup-shaped, closed and has integral therewith and depending therefrom a rod 36 of appreciable diameter on which the rotatable member 2! is supported and about which it may rotate. Secured to the rod 33 at the upper and lower end thereof and opposite the ball bearing race rings 28 and 29 are similar rings 31 and 31. In the race of said rings are provided the usual antifriction bearings.

The X-ray tube includes essentially the assembly as shown with the stationary member 29 consisting of a comparatively large chamber characterized in that the lower end thereof is in the form of a plurality of spaced annular chambers 39 which are united by being closed at their lower ends and similarly united chambers 45 are also formed which are closed at their upper ends thus forming a water tight seal. This stationary member 28 is supported by the envelope U3 and is in axial alignment with said envelope, the supporting rod 35 being coincident with the center longitudinal axis of said envelope.

The rotatable member 2| supported by the rod 35 has its outermost cylinder 23, carrying the magnetizable material surrounding and adjacent to but spaced from the cylinder 38. The remaining cylinders 24, 25 and 26 extend into the annular space 48, with the upper end of said cylinders being spaced from the corresponding portion of said spaces only a distance suflicient for safe clearance with the members defining said spaces.

The chambers 39 depend into the annular spaces 59 and are of such dimensions that the sides thereof will not, during rotation of the target, contact the walls describing said spaces. The length of the chambers defined by the cylinders extending from the rotatable member is substantially the same as the length of the chambers defined by the cylinders extending from the stationary member.

Mounted exteriorly of the tube is an appropriate winding 42 which, upon energization will cause the rotatable member 2! to rotate about the stationary member 29.

In operation, the winding G2 is energized, the filament is incandesced and the desired potential is applied between the anode and cathode by connecting one of the terminals of a high voltage source to the cathode and the other terminal to the anode. This causes rotation and electron bombardment of the target and this condition is maintained for the desired length of time and then terminated. During the operation of the tube and especially when a large current at a high voltage passes through the X-ray tube, the rotatable member becomes very hot and may attain a temperature of about 500 to 600 C. The spaced cylindrical portions thereof at this temperature radiate a great deal of heat to the stationary member 2|! because of the large radiating area represented by the cylinders 23, 24, 25 and 26 and because of the large area represented by the cylinders 30, 3!, 32, 33, 34 and 35 and because of the low temperature of said last named group of cylinders as compared to the temperature of said first named group of cylinders and further because of the close proximity of these groups of cylinders with respect to each other. A circulating or non-circulating system of water or air may be employed in the stationary member 28.

If desired, I may make the stationary member of a solid copper rod having a plurality of concentric solid copper cylinders such as those on the rotatable member in place of the chambers as shown. Further the cooling sheets or cylinders may extend in a horizontal rather than a vertical plane. The heat radiating portion of the rotatable member and the cylinders of the stationary member may be roughened and blackened to provide good heat radiating surfaces.

My invention is susceptible to various modifications and, therefore, is to be limited only by the prior art.

What is claimed:

1. An electron discharge device comprising an envelope having a thermionic cathode and an anode disposed therein, said anode comprising a stationary metallic member of good heat conducting material supported by said envelope and forming a comparatively large chamber with the lower end thereof formed into a plurality of concentrically spaced fluid tight annular chambers and a rotatable metallic member having a plurality of concentrically arranged metallic cylinders projecting toward and surrounding said annular chambers for the purpose of transmitting generated heat from said rotatable member to said stationary member during operation of said device, and means supported by said envelope and operable to cause rotation of said rotatable memher.

2. An electron discharge device comprising an envelope having a thermionic cathode and an anode disposed therein, said anode comprising a stationary metallic member of good heat conducting material supported by said envelope and forming a comparatively large chamber with the lower end thereof formed into a plurality of concentrically spaced fluid tight annular chambers and a rotatable metallic member comprising a cone of good heat conducting material provided with a target and having a plurality of concentric cylinders integral with said cone and surrounding said annular chambers for the purpose of transmitting heat to said stationary member, and means supported by said envelope and operable to cause rotation of said rotatable member.

VICTOR JOHN ANDREW. 

